Electrochemical reduction represents a potential solution for converting carbon dioxide into more valuable products. One application for the carbon dioxide reduction reaction (CO₂RR) would be carbon monoxide production, which is a valuable fuel and chemical precursor. An important challenge for commercialization of this process has been finding inexpensive catalysts with a high selectivity to carbon monoxide production. The selectivity towards carbon monoxide production is limited both by the competing hydrogen evolution reaction and poisoning caused by strong binding of carbon monoxide[1-2]. Initial work on non-precious metal CO₂RR catalysts was based on iron-based metal-nitrogen-carbon (MNC) catalysts that were originally developed for the oxygen reduction reaction but have also shown strong CO generation performance [1, 3-5]. In the present work a Nickel based MNC catalyst is shown to have higher CO-production rates and less CO-poisoning in comparison to the iron-based MNC catalysts.

In order to make this comparison, a family of catalysts is synthesized by the polymerization of nitrogen precursors around a carbon support and metal precursor [1, 6-7]. Upon heat treatment at 900 °C and subsequent acid washes, a nitrogen-rich, metal-nitrogen-carbon matrix is synthesized. These catalysts are characterized physically and electrochemically. In this work the nickel-based MNC catalyst is shown to be a significant improvement over the Fe-based catalysts and other non-precious metal alternatives. Although the iron-based catalyst shows lower onset overpotential, the nickel-based catalyst has higher peak currents and a longer lifetime.

In this work it is found that the higher current densities and longer lifetime are a result of increased resistance to CO-poisoning. Furthermore, the CO-poisoning allows in situ confirmation of active site quantification via carbon monoxide adsorption techniques. Ultimately, these findings allow optimization of MNC catalysts resulting in high performance non-precious metal catalysts for CO₂RR.

References:

[1.] Varela, A. S.; Sahraie, N. R.; Steinberg, J.; Ju, W.; Oh, H. S.; Strasser, P., Angew Chem Int Edit 2015, 54 (37), 10758-10762.

[2.] Tripkovic, V.; Vanin, M.; Karamad, M.; Bjorketun, M. E.; Jacobsen, K. W.; Thygesen, K. S.; Rossmeisl, J., J Phys Chem C 2013, 117 (18), 9187-9195.

[3.] Sahraie, N. R.; Paraknowitsch, J. P.; Gobel, C.; Thomas, A.; Strasser, P., J Am Chem Soc 2014, 136 (41), 14486-14497.

[4.] Hao, G. P.; Sahraie, N. R.; Zhang, Q.; Krause, S.; Oschatz, M.; Bachmatiuk, A.; Strasser, P.; Kaskel, S., Chem Commun 2015, 51 (97), 17285-17288.

[5.] Gong, X.; Liu, S. S.; Ouyang, C. Y.; Strasser, P.; Yang, R. Z., Acs Catal 2015, 5 (2), 920-927.

[6.] Gang Wu, K. L. M., Christina M. Johnston, Piotr Zelenay, Science 2011, 332, 443-447.

[7.] Sahraie, N. R.; Kramm, U. I.; Steinberg, J.; Zhang, Y. J.; Thomas, A.; Reier, T.; Paraknowitsch, J. P.; Strasser, P., Nature communications 2015, 6.